1. Field of the Invention
The invention relates to a moulding system, in particular a calibration die, for an extrusion plant, preferably with mutually spaced inlet and outlet faces disposed parallel with one another and side faces extending between them, in which a longitudinal axis of the object to be fed through a calibration orifice is disposed substantially perpendicular to the inlet and outlet face and a gap extends between a forming surface and a side face, at least over a part of the distance between the inlet and outlet face.
2. The Prior Art
A calibration die consisting of several assembled parts is known from patent document EP 0 990 805 A1 owned by the present applicant, in which individual parts are assembled to make up the calibration die depending on the profiled contour and these individual parts sit with mutually facing separation surfaces in abutment with one another. In order to place the individual parts in mutual alignment with one another, at least one positioning element is disposed between them, by means of which the individual parts can be positioned and re-adjusted relative to one another by varying the distance of the positioning surfaces on the positioning element. To this end and depending on the layout of the separation planes, a displacing motion is generally possible transversely to the direction of extrusion in which the object is fed through. The disadvantage of this approach is that the processing needed to produce the positioning element so that it can be mounted between parts of the calibration die, to enable mutual and individual positioning of the parts of the calibration die, is relatively complex and additional parts also have to be made for the positioning process, resulting in higher costs. Furthermore, it has not always been found possible to obtain satisfactory positioning in all applications.
Short gauges for a cooling and calibration system are known from patent specifications DE 198 06 202 C1 and EP 0 936 053 A1, comprising a calibration plate and at least one recess with a profiled cross-section provided therein and at least one calibration element which partially projects into the recess with the profiled cross-section. The object to be calibrated, in particular a hollow plastics section, is drawn through the profiled recess. At least one locking recess of the profiled cross-sectional recess is provided in the calibration plate, in which the calibration body with its locking element can be inserted. The locking element in turn comprises a lock foot element and a calibration element joined thereto, and a bolt-receiving recess is provided in the lock foot element. The locking element is also provided with another slotted recess. The locking element is retained by inserting it in the locking recess of the calibration plate and fixing on the calibration plate by means of a conical locking bolt element which is inserted in the bolt-receiving recess. The disadvantage of this approach is that the individual parts must be made to a high degree of accuracy in order to ensure perfect positioning and fixing on the calibration plate, and inadvertent loosening of the connection can not be reliably guaranteed in all types of application.
Another calibration plate for the tank of an extrusion tool is known from patent specifications AT 003 321 U1 and DE 299 06 109 U1, which is provided with at least one orifice substantially of the same shape as the profile of the extruded object to enable the extruded object to be guided through the extrusion system and kept in shape. Provided around the circumference of the orifice in the calibration plate, at points where the extruded material slides along the extrusion system, are wear-resistant inserts, which are secured in the calibration plate by means of a press-fit seating, bonded or welded connection or screw connections. The disadvantage of this approach is that it requires a considerable amount work to fix the individual inserts in place and once they have become worn, a considerable amount of effort is involved in replacing them with new inserts.
A calibration plate made up of a plurality of individual parts is known from patent specification U.S. Pat. No. 5,626,807 A, whereby individual parts of the calibration plate, in particular those needed to set up groove-shaped portions of the plastics section, are retained and fixed between the individual plate segments.